Shipbuilding Glossary for Project Managers

Gross tonnage measures a ship's enclosed volume under the 1969 Tonnage Convention; it is not a weight. In the Red Ensign Group Yacht Code, the chapters on machinery, electrical installations, steering, bilge pumping, structural fire protection, fire appliances and safety management exist in an A version for yachts under 500 GT and a B version for 500 GT and over. From 500 GT the ISM and ISPS Codes and further certificates also apply. That is why many yachts are designed to stay just below the line, and why gross tonnage is tracked as a design budget from the first GA. See rules before lines: the 500 GT decision.

In PMI usage a baseline changes only through formal change control. Microsoft Project can store up to eleven baselines, the main Baseline plus Baseline 1 to 10, so a planner can keep the contract baseline and later approved re-baselines side by side. Variance against the baseline is what owners and management read: a task late against the current plan matters less than a milestone drifting against the contract baseline. Re-baselining every month to make variances disappear defeats the purpose. In earned value management the cost baseline becomes the performance measurement baseline. See MS Project views, baselines and progress reporting.

Once the WBS says what will be done, the BOQ says how much of it there is. Each BOQ line sits under a WBS element, so quantities roll up by block, zone or system and can be multiplied by productivity norms to give man-hour and cost estimates. The BOQ is also the denominator for progress measurement: tonnes welded, metres of cable pulled or square metres coated against the total. Quantities start as estimates from the outline design and are refined as detailed engineering releases drawings and material lists. See WBS and BOQ in ship newbuilding projects.

In block construction the hull is divided into blocks whose size and weight suit the yard's cranes, transporters and workshops. Each block is built up through production stages: single plates and profiles, small groups and sub-groups, flat and curved panels, stiffened panels and sub-blocks. Block boundaries are a planning decision as much as a structural one, because they fix the work packages, the outfitting that can be done before erection and the joints that will be welded in the dock. Each block normally carries its own steel weight, man-hours and schedule. See block construction and erection sequencing and grand block.

Also called the hull block construction method, it moves work out of the dock into shops where access, lifting and welding positions are better, and lets many blocks progress at the same time. It goes together with zone outfitting, because both organise work by product and area rather than by ship system. The trade-off is precision: blocks built in different places must fit when they meet, and deviations accumulate during erection, so dimensional control at every stage matters. For the planner, the block becomes the main unit of scheduling, progress and cost. See the block construction and erection sequencing guide.

Erection is where the separate block schedules converge, which is why the hull's critical path usually runs through it. Each lift depends on the block being complete and inspected, the crane and transporter being free, and the blocks below it being aligned and welded enough to take it. After landing, the block is surveyed against the construction reference and adjusted before the erection joints are welded and tested. Dimensional acceptance before the next operation can be made a hold point in the inspection and test plan. See the block erection sequence plan and erection sequence.

The berth is where block erection takes place and the keel is laid, so its occupancy usually sets the hull's critical path and the yard's throughput. Berth time is planned per hull: how many days from first block to launch, and whether hulls can overlap in the same space. On an inclined slipway the hull is launched down sliding ways. In yard usage "berth" can also mean a quay position for afloat work, such as an outfitting berth, so it is worth checking which meaning a schedule uses. See crane and dock capacity planning.

The contract names the classification society and the notations the ship must achieve, so each notation is a scope item with its own rule chapters, drawings, equipment and tests. Some notations are assigned only at the owner's request, for example the ABS dynamic positioning notations, and add cost and survey work. Notation names differ between societies even where the requirements are similar, which matters when comparing bids or moving a specification from one society to another. If the conditions for class are not maintained, class may be suspended, withdrawn or revised to a different notation. See four classification societies compared.

During a newbuild, class reviews the design plans, attends construction at the yard, attends key component makers' works and attends trials before delivery. In service, the owner keeps the ship in class through periodical surveys. Many flag states also authorise classification societies as recognised organisations to carry out statutory surveys on their behalf. A class certificate is not a warranty of safety or seaworthiness; it attests compliance with the society's rules. IACS has twelve member societies. For planners, plan approval and survey attendance are schedule inputs, not afterthoughts. See quality assurance and classification society surveys.

PMI distinguishes contingency reserve, held within the baseline for known risks with active responses, from management reserve, held outside it for unforeseen work within scope. A register is useful only if it is reviewed and drives decisions: each risk needs an owner, a response and a trigger, and contingency should be released or reallocated as risks close. Typical newbuild entries include late long-lead equipment, design changes, rule changes after signing, productivity and supplier failure. The contract is a risk input too: the LD grace period, the cap and the rejection thresholds are limits the register should track. See risk management in shipyard new-build projects.

The WBS says what work is done; the CBS says where the money goes. The two are mapped so that each work package or control account has a budget, and actual costs from purchasing and timesheets are booked against it. PMI describes how activity estimates and contingency reserves roll up into work packages and control accounts to form the cost baseline. On a newbuild the CBS typically separates design, hull steel, machinery, outfitting, owner-furnished items, class fees and trials, so that the final account can explain each difference from the estimate. See the newbuild cost breakdown structure.

A CPI of 0.9 means each unit of money spent has earned 0.9 units of budgeted work. The cumulative CPI is widely used for forecasting: one common estimate at completion is the budget at completion divided by the cumulative CPI. Because it is a ratio, CPI should be read per work package as well as for the whole ship, since a healthy overall figure can hide one block or subcontract that is losing money. It also depends on honest measurement of earned value: overstated progress inflates CPI and hides the problem until late. See earned value management on a shipyard project and SPI.

A forward pass gives each activity its early start and finish; a backward pass from the project finish gives its late dates. The difference is float, and the chain of activities with the least float forms the critical path, the longest path through the network. On a newbuild the critical path often runs through engineering for the first blocks, long-lead equipment, block erection and the trials sequence, and it moves as work progresses, so it is recalculated at every update. CPM is only as good as its logic: missing links and hard date constraints produce a false critical path. See CPM scheduling for shipbuilding.

After successful trials the builder gives notice of readiness and the parties settle outstanding items. Minor deficiencies that do not affect safe operation are usually listed for completion after delivery, sometimes against a retention. At delivery the final instalment is paid and the builder hands over the builder's certificate, the bill of sale, class and statutory certificates, a statement that the ship is free of encumbrances, and the as-built documentation. The builder's guarantee period, usually 12 months, runs from delivery. A pre-delivery meeting that checks every contractual condition prevents surprises on the day. See sea trials and delivery.

A freeze lets the yard order materials and release production information that depend on the frozen design. Changes remain possible afterwards, but they go through a variation order with priced cost and time. A freeze is rarely one moment for the whole ship; it is usually a set of dates, each fixing one layer of the design. GAO's comparison of commercial and naval shipbuilding found that commercial builders complete key design phases, tied to a finished 3D product model, before construction starts, and that starting on an unstable design leads to out-of-sequence work and rework. See specification, GA and the design freeze.

Under IMO MSC.1/Circ.1580, equipment class 2 must withstand a single fault in any active component or system, and class 3 must also withstand failure of static components and the loss of every component in any one watertight compartment or fire sub-division. Class 3 therefore drives physical separation, with A-60 divisions between redundant systems. Class societies express these classes through their own notations, such as ABS DPS-2 or DNV DYNPOS(AUTR). A failure modes and effects analysis (FMEA) is required for classes 2 and 3 and is confirmed by proving trials, which belong in the commissioning schedule. See DP2 or DP3 in a newbuild contract.

Class plan approval checks compliance with the rules. Buyer approval checks the drawing against the specification, usually within a turnaround fixed in the contract, and some contracts treat a drawing as approved if no comments arrive in time. Late approval beyond the agreed turnaround is a typical ground for a builder's delay claim, so a drawing register with submission date, comment due date, comments received and status is the evidence both sides need. Buyer approval does not usually change the contract or relieve the yard of its obligations. See specification, GA and the design freeze and technical data package.

A graving dock is a basin built into the shore, closed by a gate and pumped dry. A floating dock is a pontoon structure that submerges, takes the ship and rises again. Newbuilds may be erected in a building dock and floated out; ships in service return periodically for hull inspection, maintenance and underwater repairs. Each docking is planned on a docking plan, which shows where the hull can safely rest on keel and side blocks. Because dock time is one of the most constrained resources in a yard, occupancy days are a central planning and commercial figure. See drydock and berth planning basics.

Planned value (PV) is the budget for work scheduled to date; earned value (EV) is the budget for the work actually done; actual cost (AC) is what that work cost. From these come cost variance (EV minus AC), schedule variance (EV minus PV) and the CPI and SPI indices. EVM needs a baselined schedule with budgets assigned to activities, and an objective measure of physical progress. Hull steel suits it well, because tonnage and hours per block are estimated early and progress is measurable. See EVM in shipbuilding.

In Microsoft Project it interacts with the task type. Fixed Work tasks are always effort-driven; for Fixed Units and Fixed Duration tasks it can be switched on or off. With it on, adding resources to a fixed-units task shortens the duration, while on a fixed-duration task it lowers each resource's units instead. That suits divisible work such as plating or cable pulling, and misleads for work that does not speed up with more people, such as a cure time, a pressure test or a class survey. Set the task type and the effort-driven flag deliberately before loading resources. See task types and effort-driven scheduling.

A typical sequence starts from a reference block, often in the engine room or midship region, and proceeds forward, aft and upward, with bottom blocks before side shell and deck blocks. Engine room blocks are often erected early so machinery can be installed and aligned before the surrounding structure closes in. The sequence works as the master production schedule: block fabrication, outfitting and painting are planned backwards from erection dates, and long-lead equipment must arrive in time for its block. IACS UR Z23 expects the yard's block plan to show how blocks are joined at pre-erection and erection. See block sequencing and critical path management.

Under UNCLOS Article 94 the flag state must effectively exercise jurisdiction and control over ships flying its flag. In practice many flag administrations delegate statutory surveys and certificates to classification societies acting as recognised organisations under the IMO RO Code, and must oversee them. The flag is chosen early because it decides which interpretations apply, which certificates must be ready at delivery and, for yachts, which code is used. Planners should know which approvals the flag keeps for itself and which the recognised organisation handles. See who does what on a yacht build.

The GA is a contract drawing, and in the usual order of precedence it ranks below the contract terms and the specification. For planners it is the master map: compartment boundaries and decks suggest zones and work packages, access routes show how equipment will be brought in, and the position of heavy machinery influences the block breakdown and erection sequence. On yachts the GA also drives gross tonnage, so late layout changes can have regulatory consequences. GA revisions after the design freeze are costly. See reading a ship's general arrangement for planners.

Grand block joining moves welding from the dock, where it is done at height and on the critical path, to the ground, where access is better and several joints can be made in parallel. Whether it pays depends on crane and transporter capacity, ground space near the dock and the erection strategy. Very large combined units are also called mega blocks; IACS UR Z23 lists sub-assembly, block, grand and mega block assembly, pre-erection and erection as stages where class checks alignment and deformation. Grand blocks also allow more pre-outfitting before erection. See building the hull block construction schedule.

HATs follow installation and commissioning and cover what can be proved without the ship under way, such as machinery protection, fire systems and many electrical and control functions. Tests that need the ship moving, such as manoeuvring and stopping, are left to sea acceptance tests or sea trials. Terms vary: many commercial contracts speak of harbour, quay or dock trials, while some naval and government contracts use HAT and SAT. Harbour testing is the filter for going to sea, because a failure found alongside is cheaper to fix than one found on a trial day with owner and class on board. See sea trials and delivery.

Both are set in the ITP together with the party concerned, such as the yard's quality department, the owner's site team or the class surveyor. IACS UR Z23 describes the class surveyor's involvement in construction as patrol, review and witness. For scheduling the difference is large: a hold point is a hard dependency, and a missed notice or an unavailable inspector stops the next activity, while a witness point needs notice but does not normally stop the work. Model hold points as activities or milestones with their notice period, not as assumptions. See quality assurance and classification society surveys.

On a newbuild the yard prepares ITPs for hull, machinery, piping, electrical and other work and agrees them with the buyer and class before the work starts. IACS UR Z23 defines class witness as attendance at scheduled inspections in accordance with the agreed inspection and test plans, so the ITP decides when a surveyor has to be called. For the planner every hold point is a schedule dependency with a notice period, and every test needs its system complete enough to be tested. ITP references also make the final quality records traceable. See quality assurance and classification society surveys.

Hogging means the middle of the hull is higher than the ends relative to the reference line; sagging means it is lower. Readings change with welding shrinkage, added weight, support settlement and temperature, so each survey records the construction stage, support condition and structural temperatures with the heights. Acceptance criteria come from the project requirements; IACS Recommendation 47 gives a standard range for whole-length deformation per 100 m against the line of keel sighting, applied as agreed with class. Surveys are scheduled around major erection and welding stages and before shaft alignment. See keel sighting and deflection surveys or use the keel deflection survey workbook.

A ship that has been "laid down" has passed this point. For IMO rules the date matters more than the ceremony: rules for ships constructed on or after a date use the keel-laying date or a similar stage of construction, meaning construction identifiable with the specific ship has begun and at least 50 tonnes or one percent of the estimated mass of all structural material, whichever is less, has been assembled. Keel laying is also a common payment milestone, so the contract should define it and class should confirm it. In the US Navy the event is called keel authentication. See planning from contract to keel laying and regulatory trigger dates.

It gives the yard a physical baseline for the hull's longitudinal geometry, usually recorded once the keel blocks are set and the first bottom blocks are landed, and repeated at later stages. Keel sighting covers a defined line or set of points, which makes it narrower than a full dimensional survey of breadth, deck heights or bulkhead positions. Survey points must be clearly marked and reproducible so that surveys taken months apart compare like with like, and the first record should document keel block heights and the support condition. The results feed the keel deflection survey. See keel sighting and deflection surveys.

In Microsoft Project a lead is entered as a negative lag, and either can be a fixed duration or a percentage of the predecessor's duration, for example SS+50% to start a task when its predecessor is half complete by duration. A percentage offset recalculates when the predecessor's duration changes; a fixed offset does not. Lags are legitimately used for real waiting time, such as paint curing, as long as the reason is recorded. A lag that hides work nobody modelled is a weakness, because the schedule cannot show progress or delay on something that is not an activity. See lag and lead time explained.

On an inclined building berth the hull is launched end-on, usually stern first, or sideways where the waterway is too narrow. Ships built in a dry dock or basin are floated out by filling the dock with water, and some yards launch on airbags. Launching is a common payment milestone, and it changes the work: from then on the hull is afloat, work below the waterline becomes harder and outfitting continues at the quay. Hull deflection also differs between the docked and afloat conditions, which is why final shaft alignment is verified afloat. See the shipbuilding project lifecycle.

Delay damages usually have three parts: a grace period with no damages, a daily rate after it, and a cap on the number of days, after which the buyer typically gains a right to cancel. Performance damages work in bands: a tolerance with no penalty, a scale of damages beyond it and a rejection threshold. This structure changes how a planner should read float. Slippage inside the grace period is commercially cheap, slippage beyond it has a known daily cost, and slippage past the cap puts the whole contract at risk. Only delays the contract treats as permissible move the delivery date, which is why delay notices matter. See how a shipbuilding contract works.

The LMAA is an association of practising arbitrators, not an institution: it does not administer arbitrations, which remain ad hoc and are run by the tribunals themselves. Its members accept appointments on the LMAA Terms, which then govern the procedure. The LMAA also publishes a Small Claims Procedure and an Intermediate Claims Procedure, both revised in 2021, for lower-value disputes. Proceedings are private; selected awards may be published in anonymised form, and the parties can object. Many newbuilding contracts choose English law and London arbitration, and some also refer technical disputes to class or an expert so the build keeps moving. See why yacht disputes go to London arbitration.

US law on Coast Guard procurement, for example, defines long lead time items as components, parts, material or effort that must be procured in advance of the production award to maintain the production schedule. On ships the usual candidates are main engines, generators, reduction gears and propellers, along with steel grades that need specific certification. Each item needs a latest safe order date worked back from its installation date, which depends on the block or space it goes into. Makers' drawings for these items also feed the design, so a late order delays engineering as well as production. See procurement for major ship equipment.

The list looks administrative but it allocates risk. If the yard chooses freely from the list and the maker is late, the delay is normally the yard's. If the buyer insists on one named maker, whose delay it is depends on how the list and the procurement obligations were written. Wording such as "or equal" gives the yard room to substitute, usually with the buyer's consent. Planners should treat the makers list as a procurement input: it fixes which vendors must supply drawings, lead times and approvals early, and it feeds the long-lead plan. See the procurement map and the makers list.

In a yard, hours are usually estimated per trade and per work package: steel hours from tonnes and weld length, pipe hours from spools and fittings, electrical hours from cable metres and terminations. Bottom-up estimates add up the lower levels of the WBS; parametric estimates apply relationships taken from previous projects. Norms have to reflect where the work is done, because the same job takes more hours inside a closed hull than on an open block. The estimate becomes the budget for earned value and the input to resource histograms and leveling. See how to estimate man-hours.

On a newbuild it typically runs from contract signing through design, procurement, steel cutting, erection, launching, trials and delivery, with the contract milestones at the top. It should be a logic-linked schedule, not a picture, so that a slip in a long-lead item or an approval shows its effect on delivery. PMI's PMBOK Guide describes a project schedule presented in summary form as a master or milestone schedule. Detailed schedules sit below it and roll up into it, and its baseline is the reference for owner reporting. See the master schedule for a yacht build.

A common pattern pays on signing, steel cutting, keel laying, launching and delivery, but the number of instalments and the share each carries are negotiated. What matters is the definition: which event, measured how, and what evidence proves it, such as a class confirmation or a joint inspection record. A vague definition is where commercial arguments start. The split also shapes cash flow: on a delivery-heavy schedule the yard finances most of the build itself, while a front-loaded schedule increases the buyer's exposure. Planners should carry each payment milestone in the schedule with its definition attached. See how a shipbuilding contract works.

BIMCO developed it partly in response to criticism that the older SAJ form lacked balance between the parties. The 2007 text is still the current edition, and BIMCO's explanatory notes are available to members only. Parties often use it as a base text and amend it, so the contract in front of you may differ clause by clause from the published form. Under NEWBUILDCON the buyer generally cannot withhold instalments, except by setting assessed liquidated damages against the final one. For a planner the important parts are the delay notice rules and the change mechanism, because they decide which slips become claims. See standard contracts in newbuilding and repair.

On-unit outfitting assembles equipment, pipes and fittings into packages on a common foundation, independent of the hull structure, for example a pump set with its valves. On-block outfitting fits units and single items onto a block or grand block before erection. On-board outfitting installs what remains inside the erected hull, in the dock or afloat at the outfitting quay, where access is most constrained. Zone outfitting aims to move as much work as practical from on-board to the earlier stages, leaving on-board work for connections between zones, large items and commissioning. See outfitting and systems integration and pre-outfitting.

At tender stage the outline specification and the general arrangement are the two documents a yard prices. A workable structure follows the way the ship will later be priced, built and tested, so bids can be compared line by line and each item can later be traced to a specification clause and a test. A thin outline specification pushes risk into the contract stage, where the gaps tend to return as variation orders. After signing it is developed into the contract or building specification. See from design brief to yard shortlist.

On superyacht builds this is usually a dedicated, independent role that verifies milestones, manages defect lists and enforces change-order discipline. On commercial ships the same function normally sits with the buyer's site team, led by a site manager or chief superintendent. Either way the authority is limited by the contract: the representative can comment, reject work that does not meet the specification and witness tests, but cannot change the contract, and approval of a detail does not usually relieve the yard of its obligations. Comments should be made promptly, in writing, and kept in a register with status and answer. See the owner's representative.

OFE, also called buyer's supplies, creates an interface the contract has to define precisely: what arrives, when, in what condition, with which documents, and who installs, commissions and answers for its performance. Late or defective OFE is normally treated as a buyer's delay, which can give the yard extra time and money, so OFE delivery dates belong in the master schedule just like the yard's own procurement, with receipt inspections recorded. Builder's guarantees usually exclude OFE, so the owner pursues defects with its own supplier. On yachts, tenders, water toys, art and specialist systems are typical OFE. See the yacht procurement map and long-lead items.

Each activity or work package carries a weight, often based on its budgeted hours or value, and earns credit by an agreed rule: units completed, steps reached within the task, or a measured percentage. Summing weight times percentage complete gives the progress of a block, a system or the whole ship. The rule of credit must be agreed in advance and backed by evidence, otherwise two parties will measure the same work differently. Physical progress is the basis of earned value and of the S-curve in the owner report. See measuring progress and the weekly owner report.

Work on an open block, often turned upside down so that overhead items can be fitted downhand, is easier to reach and safer than the same work in a closed compartment, and it shortens time in the dock. The price is earlier design information: piping and cable details, equipment layouts and makers' drawings must be released before the block is built, and a late change costs more on a heavily outfitted block. Pre-outfitting also has to be sequenced with blasting and coating, and finished before shell or deck plating closes the access. See pre-outfitting strategy and outfitting stages.

Title to the hull normally stays with the builder until delivery, so every instalment paid before then depends on the yard's performance and solvency. The refund guarantee is the buyer's security, and contracts commonly make the pre-delivery instalments payable only once an acceptable guarantee has been issued. The wording matters as much as the guarantee itself: whether it pays on demand or only after an arbitration award decides how quickly the money comes back. BIMCO published a standalone refund guarantee form in 2021, intended for use with NEWBUILDCON, the SAJ form and Chinese forms. Read more in how a shipbuilding contract works.

Classification societies apply the rule edition in force on the date of contract for construction, as defined in IACS Procedural Requirement 29. Most IMO construction rules apply to ships whose keel is laid, or which are at a similar stage of construction, on or after a stated date. Some newer measures use all three dates, so a late delivery can pull a contracted ship into a new requirement. Since March 2026 the record of construction attached to the IAPP certificate lists the contract, keel-laying and delivery dates separately. Planners should put the relevant cut-offs in the master schedule next to the contract milestones. See which rules apply to your newbuild.

Repair work differs from a newbuild because the scope is not fully known at signing: opening tanks, blasting the hull or dismantling machinery reveals extra work. Repair contracts therefore rely on unit rates, day rates and fast approval of additional items rather than a single fixed price, and a late redelivery keeps an earning ship out of service and can block the dock for the next vessel. REPAIRCON gives owner and yard a common text for that situation. For the planner, the inputs are the repair specification, the agreed rates and the docking schedule. See planning a ship repair drydocking and drydock.

Microsoft Project levels by delaying or splitting tasks and assignments, choosing what to move from the leveling order, dependencies, priorities and constraints; tasks with Must Start On or Must Finish On constraints or an actual start are generally not moved. Leveling only within available slack protects the finish date but often resolves little. Resource smoothing is the gentler variant that uses float only. In a yard the scarce resources are often cranes, dock space, panel line capacity or a test team, and these should be modelled as resources too. Always review automatic results with production. See resource leveling and crane/dock capacity planning.

The shape follows from how work ramps up, peaks and tails off. PMI describes the time-phased cost baseline as typically displayed as an S-curve. In progress reporting, the planned curve from the baseline is plotted with the actual or earned curve, and the gap shows whether the project is ahead or behind. Separate curves for engineering, steel, outfitting and commissioning show what a single combined curve can hide. The term is also used for the cumulative probability curve produced by a schedule or cost risk analysis. See measuring progress and the weekly owner report.

Because it was drafted by a builders' association, the SAJ form is generally regarded as favouring the yard, and buyers usually negotiate amendments. It has also served as the starting point for contract forms used in South Korea, China, Taiwan and Singapore, so many Asian yard forms will look familiar to anyone who knows it. Instalments fall due on milestones and the buyer cannot hold them back because of a dispute. The builder must notify a permissible delay within a short period of the event, and late notice weakens the claim. Clause numbers and periods vary between amended versions, so read your own text. Compare it with NEWBUILDCON in standard contracts in newbuilding and repair.

A typical programme includes speed runs, an endurance run, manoeuvring and turning tests, a crash stop, steering gear and anchoring trials, with class attending the items its rules require. The results feed the contract's performance guarantees, so trial conditions, measurement methods and corrections, for example under ISO 15016 for speed and power trials, are agreed well before the ship sails. The trial agenda should state acceptance criteria and who decides pass or fail. Deficiencies are sorted by whether they block class, block safe delivery or can be completed after delivery. See sea trials and delivery and the sea trial checklist.

Most commercial newbuilds are sold at a fixed lump-sum price paid in milestone instalments, with the buyer's pre-delivery money secured by a refund guarantee. The contract is really a set of documents: the commercial terms, the technical specification, the contract drawings and the makers list, with an order of precedence for when they disagree. For planners, the clauses that matter day to day are the delivery date, permissible delay and its notice periods, liquidated damages, modifications and trials. Each one becomes a register or a date in the schedule. Contracts are usually based on a standard form such as SAJ or NEWBUILDCON and amended in negotiation; see standard contracts in newbuilding and repair.

SPI measures schedule performance in value terms across all work, which makes it useful at programme level where many late and early activities offset each other on the Gantt chart. It has two limits. It does not know which work is critical, so an SPI near 1.0 can sit alongside a slipping critical path. And because earned value and planned value both reach the total budget when the work is finished, SPI returns to 1.0 at completion even on a late project. Read it together with float and milestone dates. See earned value on a shipyard project.

Plates and profiles are normally shot-blasted and given a shop primer on the preparation line, then cut and formed. The cut parts flow into small groups, panels and sub-assemblies and finally into blocks. Where steel cutting is a payment milestone, the contract should define what counts, for example the first cut of hull steel for that hull number, and what proves it, such as a record attended by class or the buyer. For planners, steel cutting is only real if engineering has released cutting information for the first blocks and steel of the required grades and certificates is in stock. See building the hull block construction schedule.

Microsoft Project has eight constraint types. As Soon As Possible and As Late As Possible are flexible, and ASAP is the default when scheduling from the project start. Start No Earlier Than, Start No Later Than, Finish No Earlier Than and Finish No Later Than are semi-flexible. Must Start On and Must Finish On are inflexible and pin the task to a date. A Start No Earlier Than tied to a confirmed equipment delivery is a fair use; hard constraints added to make bars sit in the right place break the critical path. For contractual dates a deadline is usually better, because it flags a miss without overriding logic. See task constraints in MS Project.

Finish-to-start (FS), the default in Microsoft Project, means the successor cannot start until the predecessor finishes. Start-to-start (SS) means it cannot start until the predecessor starts. Finish-to-finish (FF) means it cannot finish until the predecessor finishes. Start-to-finish (SF) means it cannot finish until the predecessor starts; PMI notes that SF is very rarely used. Real shipyard work overlaps, so a schedule built only from FS links tends to overstate duration. Every activity except the first and last should have at least one predecessor and one successor. See task dependencies in MS Project and lag and lead.

The term comes from defence acquisition, where the US standard MIL-STD-31000 sets out what a TDP contains, but the idea applies to any newbuild. One half of the package describes intent: drawings, 3D model extracts, specifications and calculations. The other half proves what was built: test records, inspection sign-offs and certificates, each traceable to a procedure revision and a location on the ship. Document control keeps both halves at the right revision and status, from issued for approval to as-built. The as-built package is part of what the owner receives at delivery. See document control and technical data packages.

Microsoft Project calls it total slack. Free float is narrower: the time an activity can slip without delaying the early start of any successor. Float belongs to a path rather than to one activity, so when one task uses it, the others on that path lose it. Negative float means the schedule as drawn already misses a constraint or deadline. On a newbuild, float against the contractual delivery date has a commercial value because of the liquidated damages structure, and recording the float consumed alongside each delay or non-conformity shows how much margin remains. See PMI-SP schedule planning and development.

Changes come from three sources: the buyer's own modifications, class rules or regulations that become mandatory after signing, and builder proposals such as an equipment substitution. Under some forms the builder need not start a buyer's modification until price and time are agreed, so many contracts add a route for disputed variations so work can continue. The recurring trap is the informal instruction: a superintendent asks for something on board, it gets built, and months later there is a claim nobody signed. The usual control is a VO register (request, proposal, agreed price and time, status) and a rule that no unsigned change is built. See variation order processes and cost impact.

Shipbuilding uses two kinds. A system-oriented WBS follows ship functions such as hull structure, propulsion and electrical. A product-oriented WBS follows how the ship is built: zones, blocks, units and stages, with hull construction, outfitting and painting as the main types of work. The two can be mapped to each other, because owners and estimators often think in systems while production works in zones. Whatever structure is chosen, its codes should link to the schedule activities, the bill of quantities and the cost breakdown structure. See building the newbuild WBS.